1. Field of the Invention
The present invention relates to mechanical sound reproduction mechanisms. As is known to those skilled in the art, such mechanisms directly or mechanically connect the needle with the speaker diaphram such that vibrations of the needle as a consequence of engaging the record grooves are transferred to the diaphram thereby vibrating the latter to cause an audible reproduction of the recorded message.
More specifically, the present invention relates to such mechanical sound reproduction mechanisms in devices of the type adapted to present an audio-visual program. Such devices permit viewing or projection of a transparency image and provide an accompanying sound presentation consisting of separate messages which are audibly reproduced in synchronization with the display of the respective image transparencies.
2. The Prior Art
Audio-visual devices of the type generally referred to are known in the prior art. In this regard, reference is made to U.S. Pat. No. 3,484,160 in the names of Marvin I. Glass and Gunars Licitis and assigned to Marvin Glass & Associates. The device shown in this patent is in the form of a stereoscopic viewer with mechanical sound reproduction means. This device is adapted to receive an audio-visual unit of the type shown in U.S. Pat. No. 3,432,230 in the names of Marvin I. Glass and Gunars Licitis and also assigned to Marvin Glass & Associates. Such audio-visual unit consists of a disc mounting a plurality of transparency pairs (for stereoscopic viewing) in a circular or annular pattern and a record which is co-axially mounted on such disc for rotation relative thereto.
According to the operation of the device shown in U.S. Pat. No. 3,484,160, an advance lever is manually operated for intermittently rotating the disc thereby to present the transparency pairs in seriatim for stereoscopic viewing. After the selected pair of transparencies is placed in viewing position by operation of the advance lever as just described, another lever or bar is manually operated to bring the sound reproduction mechanism into engagement with the record for audibly reproducing the message corresponding to the transparency pair being viewed. Thus, according to the operation of this prior art device, it is necessary for the operator to actuate two separate levers in the proper sequence to present the audio-visual program.
According to the device disclosed in U.S. Pat. No. 3,484,160, the speaker diaphram is engaged by the tone-arm intermediate the ends of the latter. One end of the tone-arm supports the needle and the other end of the tone-arm is pivoted to permit the necessary movement of the needle as it moves radially with respect to the record. Consequently, the point of engagement between the speaker and the tone-arm moves during movement of the needle from the outermost portion of the record to the innermost portion thereof. In other words, during most of the audio presentation, the speaker is engaged by the tone-arm at a point which is eccentric to the speaker cone. This eccentric speaker engagement is not conducive to optimum speaker operation.